linux-kernel - Re: [linux-pm] [PATCH] ACPI: replace strlen("string") with sizeof("string") -1

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Message-ID: <Pine.LNX.4.44L0.1208061556010.1649-100000@iolanthe.rowland.org>
Date:	Mon, 6 Aug 2012 15:59:37 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Vasilyev <pavel@...linux.ru>
cc:	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
	<linux-acpi@...r.kernel.org>,
	<linux-pm@...ts.linux-foundation.org>,
	<linux-kernel@...r.kernel.org>, Len Brown <len.brown@...el.com>
Subject: Re: [linux-pm] [PATCH] ACPI: replace strlen("string") with
 sizeof("string") -1

On Mon, 6 Aug 2012, Pavel Vasilyev wrote:

> >> http://www.gossamer-threads.com/lists/engine?do=post_attachment;postatt_id=41157;list=linux
> >
> > Interestingly, many (all?) of the changes in that patch are wrong
> > because they don't try to match the terminating '\0'.  As a result,
> > they will match against extensions of the target string as well as the
> > target string itself.
> >
> 
> strNcmp compare N bytes - http://lxr.linux.no/#linux+v3.5/lib/string.c#L270
> memcmp compare N bytes  - http://lxr.linux.no/#linux+v3.5/lib/string.c#L651

Yes.  So if s contains "abcde" then

	memcmp(s, "abc", 3) and strncmp(s, "abc", 3) will both return 0, and
	memcmp(s, "abc", 4) and strncmp(s, "abc", 4) will both return 1.

Alan Stern

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